Drive arrangement for a bicycle, having a greater difference in the number of teeth between the largest and the smallest rear chain sprocket

Abstract

A drive arrangement for a bicycle including a chainring having a chainring axis, a plurality of different rear sprockets, the plurality of rear sprockets sharing a sprocket axis, a drive chain that runs around the rear sprockets and the chainring and in meshing engagement with a selected active sprocket of the plurality of rear sprockets and the chainring, and a rear derailleur. The rear derailleur is configured to shift the chain over a plurality of sprockets having a difference in tooth count of over 25 teeth ranging from a smallest to a largest sprocket.

Description

BACKGROUND OF THE INVENTION[0001]A drive arrangement for a bicycle is known, for example, from U.S. Pat. No. 3,748,916. This known drive arrangement describes a rear chain guide. The rear chain guide has a chain guide roller that is disposed, with reference to an active sprocket, tangential to a next-larger inactive sprocket, in order to improve the shifting process. In the sense of the present application, a chain guide roller that is positioned by the chain guide closer to the sprocket is the chain guide roller off which the drive chain, rotating in the drive direction, last runs before it runs onto the active rear sprocket as viewed in the direction of the sprocket axis.BRIEF SUMMARY OF THE INVENTION[0002]The present invention relates to a drive arrangement for a bicycle. The drive arrangement includes a front chainring that can rotate about a chainring axis. A plurality of coaxial rear chain sprockets is provided having different diameters and different numbers of teeth. A drive...

AI Technical Summary

Benefits of technology

[0004]For reliable and reproducible shifting at the rear chain sprockets, in other words for shifting the drive chain from an active chain sprocket that is currently in meshing engagement with the drive chain to a currently inactive destination sprocket that is to be active in the future, it is advantageous if the free chain section between the chain guide roller that is closer to the sprocket (i.e., a first guide roller) and the rear chain sprocket is not too long. Otherwise, an axial movement of the rear derailleur parallel to the common sprocket axis of the rear chain sprockets tends to lead to curvature of the chain rather than to shifting it from an active sprocket to an adjacent inactive destination sprocket. Likewise, this free chain length should not be too short. Otherwise, the drive chain, which is usually configured as a roller chain, with inner and outer plates, acts like a rigid solid body. In this condition, the rear derailleur may jam the free chain piece between the first chain guide roller and the sprocket, instead of shifting the chain to an adjacent chain sprocket.

[0035]In this connection, the difference in the number of teeth between the rear sprocket with the most teeth and the rear sprocket with the least teeth can easily amount to more than 25 teeth. Differences in the number of teeth of more than 28 teeth between the largest rear sprocket and the smallest rear sprocket can also be reliably implemented. Even differences in the number of teeth of more than 30 teeth are possible. Most preferred is a difference of 32 teeth, which allows the implementation of not only gear reductions but also gear increases between the chainring and the active chain sprocket, so that such a drive arrangement can be used not only for uphill riding, but also for riding on level terrain and for fast downhill riding.

Problems solved by technology

In this connection, a shifting process in which the drive chain is supposed to be shifted from an active sprocket to an inactive chain sprocket that is larger in diameter is particularly problematic, because the chain must rise from the currently active sprocket to the inactive chain sprocket having the larger diameter.

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